On Tue, Nov 16, 2021 at 4:03 AM Richard Henderson <
richard.hender...@linaro.org> wrote:
> From: Warner Losh <i...@bsdimp.com>
>
> FreeBSD system calls return positive errno. On the 4 hosts for
> which we have support, error is indicated by the C bit set or clear.
>
> Signed-off-by: Warner Losh <i...@bsdimp.com>
> [rth: Rebase on new safe_syscall_base api; add #error check.]
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> common-user/host/aarch64/safe-syscall.inc.S | 12 +++++++++++-
> common-user/host/arm/safe-syscall.inc.S | 11 +++++++++++
> common-user/host/i386/safe-syscall.inc.S | 10 ++++++++++
> common-user/host/x86_64/safe-syscall.inc.S | 10 ++++++++++
> 4 files changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/common-user/host/aarch64/safe-syscall.inc.S
> b/common-user/host/aarch64/safe-syscall.inc.S
> index 95c60d8609..d3f065cdef 100644
> --- a/common-user/host/aarch64/safe-syscall.inc.S
> +++ b/common-user/host/aarch64/safe-syscall.inc.S
> @@ -65,12 +65,22 @@ safe_syscall_start:
> safe_syscall_end:
>
> /* code path for having successfully executed the syscall */
> - cmn x0, #4095
> +#if defined(__linux__)
> + /* Linux kernel returns (small) negative errno. */
> + cmn x0, #4096
> + b.hi 0f
> +#elif defined(__FreeBSD__)
> + /* FreeBSD kernel returns positive errno and C bit set. */
> b.cs 1f
> +#else
> +#error "unsupported os"
> +#endif
> ret
>
> /* code path setting errno */
> +#ifdef __linux__
> 0: neg w0, w0 /* create positive errno */
> +#endif
> 1: str w0, [x11] /* store errno */
> mov x0, #-1
> ret
> diff --git a/common-user/host/arm/safe-syscall.inc.S
> b/common-user/host/arm/safe-syscall.inc.S
> index 17839c6486..328299021d 100644
> --- a/common-user/host/arm/safe-syscall.inc.S
> +++ b/common-user/host/arm/safe-syscall.inc.S
> @@ -82,12 +82,23 @@ safe_syscall_start:
> safe_syscall_end:
>
> /* code path for having successfully executed the syscall */
> +#if defined(__linux__)
> + /* Linux kernel returns (small) negative errno. */
> cmp r0, #-4096
> bhi 0f
> +#elif defined(__FreeBSD__)
> + /* FreeBSD kernel returns positive errno and C bit set. */
> + bcs 1f
> +#else
> +#error "unsupported os"
> +#endif
> +
> 9: pop { r4, r5, r6, r7, r8, r9, r10, pc }
>
> /* code path setting errno */
> +#ifdef __linux__
> 0: neg r0, r0 /* create positive errno */
> +#endif
> 1: str r0, [r9] /* store errno */
> mov r0, #-1
> b 9b
> diff --git a/common-user/host/i386/safe-syscall.inc.S
> b/common-user/host/i386/safe-syscall.inc.S
> index ad89521783..a9382f777e 100644
> --- a/common-user/host/i386/safe-syscall.inc.S
> +++ b/common-user/host/i386/safe-syscall.inc.S
> @@ -76,8 +76,16 @@ safe_syscall_start:
> safe_syscall_end:
>
> /* code path for having successfully executed the syscall */
> +#if defined(__linux__)
> + /* Linux kernel returns (small) negative errno. */
> cmp $-4095, %eax
> jae 0f
> +#elif defined(__FreeBSD__)
> + /* FreeBSD kernel returns positive errno and C bit set. */
> + jcs 1f
>
I needed to change this to 'jc' and that's all google found for Intel.
+#else
> +#error "unsupported os"
> +#endif
>
> 9: pop %ebx
> .cfi_remember_state
> @@ -97,7 +105,9 @@ safe_syscall_end:
> .cfi_restore_state
>
> /* code path setting errno */
> +#ifdef __linux__
> 0: neg %eax /* create positive errno */
> +#endif
> 1: mov 8+16(%esp), %ebx /* load errno pointer */
> mov %eax, (%ebx) /* store errno */
> mov $-1, %eax
> diff --git a/common-user/host/x86_64/safe-syscall.inc.S
> b/common-user/host/x86_64/safe-syscall.inc.S
> index 9a0c4c93b4..36b7efe2ca 100644
> --- a/common-user/host/x86_64/safe-syscall.inc.S
> +++ b/common-user/host/x86_64/safe-syscall.inc.S
> @@ -75,8 +75,16 @@ safe_syscall_start:
> safe_syscall_end:
>
> /* code path for having successfully executed the syscall */
> +#if defined(__linux__)
> + /* Linux kernel returns (small) negative errno. */
> cmp $-4095, %rax
> jae 0f
> +#elif defined(__FreeBSD__)
> + /* FreeBSD kernel returns positive errno and C bit set. */
> + jcs 1f
>
Likewise.
> +#else
> +#error "unsupported os"
> +#endif
>
> 9: pop %rbp
> .cfi_remember_state
> @@ -86,7 +94,9 @@ safe_syscall_end:
> .cfi_restore_state
>
> /* code path setting errno */
> +#ifdef __linux__
> 0: neg %eax /* create positive errno */
> +#endif
> 1: mov %eax, (%rbp) /* store errno */
> mov $-1, %rax
> jmp 9b
>
I've not yet tested this on my arm/aarch64 systems, but I think it will
work there.
Warner
